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Bonnie Gray and Ajit Khosla

Bonnie Gray (left) and Ajit Khosla stretch their flexible electrically conductive polymer for new microchip applications.

Rubbery microchips no stretch

January 22, 2009

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By Barry Shell

Last November, engineering science student Ajit Khosla handed his PhD supervisor Bonnie Gray a rubbery five-centimeter diameter disk produced as a result of his ongoing thesis research.

"I was sitting there playing with it, stretching it and twisting it while he showed me his experimental results," says Gray. The data were remarkable. The material conducted electricity like some metals but it could be tied in knots.

"I think we can publish this," Gray said, to which Khosla replied, "Can we actually patent it?"

Khosla came to SFU to research lab-on-a-chip technology, a way to do chemistry and biology on microchips with tiny amounts of liquid. These systems typically sit on rigid glass or silicon chips. But Gray had been studying thin, flexible plastic polymer substrates made of silicone, which made wearable electronics and biomedical implants possible.

Gray had already developed methods for connecting microscopic fluid-carrying tubes, but her tiny metallic electrical connections would snap when the devices were flexed. So she asked Khosla to come up with something better.

He tried mixing metal powders into the polymers to make them conductive, testing at least 25 different substances. "I even bought graphite at Canadian Tire and tried that," says Khosla. Eventually, he discovered that a blend of 35 per cent nano-silver and several polymer chemicals resulted in good conductivity, high flexibility and micro-mouldability. The pair received a provisional patent for their invention in December 2008.

"The material conducts electricity better than any other flexible conducting polymer we have seen published or patented," says Gray. "As a microfluidics and micromechanical systems researcher, I am very excited about all the things we can do with this."

The duo envisions countless applications for the new technology, such as contact lenses with embedded microfluidics and microelectronics or surgically implanted electronic pressure sensors for studying knee joints. Already, they’re developing a bra with flexible sensors to screen for breast cancer.

"We’re going to eventually use this for everything," says Gray.

Improving the new polymer and completing his PhD will take years, says Khosla. "Right now I’m really excited about using silver nano-rods," he says, referring to a new form of silver that will hopefully increase conductivity even more.

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